In the field of wireless communication, the terms “User Equipment, UE” and “wireless device” are commonly used for various communication entities e.g. including mobile telephones, tablets and laptop computers. In this disclosure, “wireless device” will be used to represent any wireless communication entity capable of communicating radio signals with a wireless network. It should be noted that a wireless device in this context may also be a Machine Type Communication, MTC, device such as a sensor, counter or measuring device arranged to operate automatically and send reports or other messages to some central node.
Further, the term “network node” represents any node of a wireless network that is arranged to communicate radio signals with wireless devices. Throughout this disclosure, the term network node is interchangeable with base station, transmission point, radio node, eNodeB or eNB, and the term wireless device is interchangeable with UE. In a typical cellular network, which is an example of a wireless communication network, User Equipments (UEs), communicate via a Radio Access Network (RAN) to one or more Core Networks (CNs).
For example, the LTE (Long Term Evolution) radio technology specified by 3GPP (3rd Generation Partnership Project) uses Orthogonal Frequency Division Multiplexing (OFDM) for downlink (DL) transmissions to UEs and Discrete Fourier Transform (DFT) spread OFDM, also referred to as Single Carrier (SC) OFDM, for uplink (UL) transmissions from the UEs. In this case, the available resources may be organized in a time-frequency grid of subcarriers with 15 kHz width and time elements corresponding to the duration of one OFDM symbol. A resource element may then extend over one subcarrier in the frequency domain and the duration of one OFDM symbol in the time domain. Such a time-frequency grid may be defined individually for each antenna port.
In the time domain, LTE DL transmissions are organized in radio frames of 10 ms duration, each radio frame consisting of ten equally-sized subframes of 1 ms duration, also referred to as TTI (Transmission Time Interval). The subframes are in turn divided into two slots, each having 0.5 ms duration. Each subframe includes a number of OFDM symbols which may be used for conveying control information or data.
The resource allocation in LTE is accomplished on the basis of resource blocks. A resource block corresponds to one slot in the time domain and 12 contiguous subcarriers in the frequency domain. In LTE, the highest granularity level of assigning resource elements corresponds to two in time consecutive resource blocks, also referred to as a resource block pair or Physical Resource Block (PRB). A PRB thus extends over the entire time duration of the subframe.
The use of LTE carrier aggregation (CA), introduced in LTE Rel-10 and enhanced in Rel-11, offers means to increase the peak data rates, system capacity and user experience by aggregating radio resources from multiple carriers that may reside in the same band or different bands and, for the case of inter-band TDD CA, may be configured with different UL/DL configurations. In Rel-12, carrier aggregation between TDD and FDD serving cells is introduced to support UE connecting to them simultaneously.
In Rel-13, LAA (Licensed-Assisted Access) has attracted a lot of interest in extending the LTE carrier aggregation feature towards capturing the spectrum opportunities of unlicensed spectrum in the 5 GHz band. WLAN operating in the 5 GHz band nowadays already supports 80 MHz in the field and 160 MHz is to follow in Wave 2 deployment of IEEE 802.11ac. There are also other frequency bands, such as 3.5 GHz, where aggregation of more than one carrier on the same band is possible, in addition to the bands already widely in use for LTE. Enabling the utilization of at least similar bandwidths for LTE in combination with LAA as IEEE 802.11ac Wave 2 will support calls for extending the carrier aggregation framework to support more than 5 carriers. The extension of the CA framework beyond 5 carriers was approved to be one work item for LTE Rel-13. The objective is to support up to 32 carriers in both UL and DL.
Compared to single-carrier operation, a UE operating with CA has to report feedback for more than one DL component carriers. Meanwhile, a UE may have different capabilities in aggregating carriers in the UL and the DL. One special case is that a UE does not need to support DL and UL CA simultaneously. For instance, the first release of CA capable UEs in the market only supports DL CA but not UL CA. This is also the underlying assumption in the 3GPP RAN4 standardization. Therefore, an enhanced UL control channel, i.e. Physical Uplink Control Channel, PUCCH, format 3 was introduced for CA in Rel-10.
Channel-state information (CSI) is used to provide the eNB with an estimate of the channel properties as seen from the terminal to aid channel-dependent scheduling. Two kinds of CSI reporting modes are supported in LTE: periodic CSI reporting and aperiodic CSI reporting. Periodic CSI can be transmitted either on PUCCH or PUSCH (Physical Uplink Shared Channel) while aperiodic CSI can only be transmitted on PUSCH. Periodic CSI consists of rank indicator (RI), wideband/sub-band PM and wideband/sub-band CQI and is reported in a periodic manner. In carrier aggregation, periodic CSI is reported for each component carrier. When periodic CSI reporting for different component carriers collide, the one with highest priority will be reported and the others will be dropped.
Periodic CSI reporting and HARQ-ACK feedback (HARQ: Hybrid Automatic Repeat Request) may occur in the same subframe. Simultaneous transmission of periodic CSI and HARQ-ACK is allowed using format 2a/b if there is only 1 or 2 bits HARQ-ACK.
When there are more HARQ-ACK bits, multiplexing of the two is treated differently in different releases.
In Rel-10, multi-cell HARQ-ACK via PUCCH Format 3 or PUCCH Format 1b with channel selection was introduced. When periodic CSI is to be reported in a subframe where multi-cell HARQ-ACK feedback is to be transmitted, periodic CSI report will be dropped, which reduces link adaptation accuracy and user throughput.
In Rel-11, periodic CSI and multi-cell HARQ-ACK (including SR) can be transmitted together via PUCCH Format 3. However, the periodic CSI for only one serving cell can be reported and others will be dropped. The basic principle of transmission of HARQ-ACK together with a single periodic CSI report is that periodic CSI use the remaining bits after HARQ-ACK feedback bits (including SR) has been assigned. The serving cell for periodic CSI reporting is selected according to the Rel-10 priority rule. This is further discussed with respect to FIG. 4.
In view of the above, there is a need for concepts with which control data, particularly control data of different types, are communicated efficiently between nodes of a wireless communication network, such as a network nodes (e.g. eNBs) and wireless devices (e.g. UEs). There is also a need to provide concepts to efficiently support an increasing number of component carriers.